In prior art, a liquid detergent (softening agent, softener and sterilizing solution) is put into the specified vessel beforehand of electric washing machine and electric dishwasher by users, then fed into the washing bucket by washing equipment by means of water washing or other mechanical method according to the washing process. By such method, the dosing quantity of detergent depends on users' operation, and detergent should be fed into vessel each washing time. With the increase of liquid detergent, it is a trend to put plenty of detergent into washing equipment, by this method, users can dose certain amount of detergent into washing equipment during washing process according to demands, to reduce operation steps, and automatically adjust dosing quantity of detergent according to types and quantity of washes. Therefore, it is a development trend to equip an automatic dosing device into the washing machine.
Japan Patent Office (JPO) 61-172594 disclosed that air pump can exert certain pressure to control the opening time of valve to control the dosing quantity of liquid detergent filled in the washing machine vessel. JPO 2000-334197 disclosed that the liquid detergent filled in the vessel can be extruded by exerting pressure to detergent. In these solutions, users need to fully seal the groove cover after liquid detergent is filled into liquid detergent groove. In case of poor sealing, the pump pressure leakage will occur. Even if the pump pressure is same, liquid detergent of different viscosity will be different in flow velocity under same pressure, leading to inaccurate dosing quantity. In addition, the pump noise will affect noise index control of washing equipment.
In Chinese markets, some washing equipments are equipped with liquid detergent tanks at the bottom. The liquid detergent is fed or sucked to water tank at top of washing equipment by pressure produced by gear pump, then to the washing bucket. In this solution, the gear pump is often immersed into the detergent, after detergent runs out, the residual detergent in pump will be dry and solidified, when using the washing machine again, more damping will hinder rotation of gear in gear pump. The work noise in gear pump can't better control noise indexes of washing equipment. In addition, this solution has dosing errors due to dosing speed difference resulting from detergent viscosity fluctuation.
JPO 11-019391 provides a solution, namely, a water pump is equipped in the washing machine, the water pump sucks water from washing bucket of washing machine or bathing pool to a nozzle on pipeline of washing bucket, a negative pressure generator is installed on the nozzle, when water flows out of the pump, the negative pressure of nozzle can suck the detergent to main water flow, then to washing bucket after mixing. The power in this technology can prevent sealing problem of air pump power solution and solidification of residual detergent in gear pump solution, but a constant-pressure water pump should be equipped, which leads to higher cost.
CN201258409Y document discloses the device that can produce negative pressure by water flow, but the negative pressure is produced through flow of tap water, and negative pressure is closely related to tap water pressure and flow, therefore, the negative pressure resulting from water dosing of solenoid valve in washing equipment changes greatly, the detergent dosing precision can't be controlled easily.
In Example 1, in order to overcome the above problems, the detergent filling measurement box sucks the detergent by residual negative pressure in measurement box under the premise of cutoff of negative pressure source and measurement box space, and if the negative pressure is inadequate, the measuring space can't be filled to the full, leading to low dosing precision, if the measuring box is not sealed well, the dosing error will be bigger. Additionally, the detergent filled in measuring box is sucked to main water flow by negative pressure, therefore, the detergent will be left over between valve and pipeline, and these concentrated or solidified detergents will hinder flow of detergent, possibly affecting the dosing effect.
A liquid detergent dosing device disclosed in CN 103397496A comprises a main passage, a valve A, a valve B, a valve C, a valve D, a liquid collection chamber, a backflow passage and a Venturi negative pressure generator. The structure is characterized by simple structure, small volume, easy to install and use, high dosing precision of detergent and detergent not easy to remain. But in this device, the water/detergent mixed liquid flows through outlets of valve C or valve C and valve D, then into liquid collection chamber, liquid in liquid collection chamber flows to Venturi negative pressure generator through backflow passage, outlet of Venturi negative pressure generator connects to inlet of main passage. Therefore, during process of water/detergent mixed liquid flowing through main passage to washing bucket, partial mixed liquid will flow through inlet section of valve A (bypassing with main passage) to circulation area where detergent doses, leading to dosing quantity error or poor dosing efficiency. In addition, the liquid collection chamber in this device is relatively big, dosing efficiency of water/detergent mixed liquid resided in liquid collection chamber is relatively low, the mixed liquid can't be easily fed by washing in a short time.